The quilt patch titled Subject: mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock has been removed from the -mm tree. Its filename was mm-kmemleak-avoid-deadlock-by-moving-pr_warn-outside-kmemleak_lock.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: Breno Leitao leitao@debian.org Subject: mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock Date: Thu, 31 Jul 2025 02:57:18 -0700
When netpoll is enabled, calling pr_warn_once() while holding kmemleak_lock in mem_pool_alloc() can cause a deadlock due to lock inversion with the netconsole subsystem. This occurs because pr_warn_once() may trigger netpoll, which eventually leads to __alloc_skb() and back into kmemleak code, attempting to reacquire kmemleak_lock.
This is the path for the deadlock.
mem_pool_alloc() -> raw_spin_lock_irqsave(&kmemleak_lock, flags); -> pr_warn_once() -> netconsole subsystem -> netpoll -> __alloc_skb -> __create_object -> raw_spin_lock_irqsave(&kmemleak_lock, flags);
Fix this by setting a flag and issuing the pr_warn_once() after kmemleak_lock is released.
Link: https://lkml.kernel.org/r/20250731-kmemleak_lock-v1-1-728fd470198f@debian.or... Fixes: c5665868183f ("mm: kmemleak: use the memory pool for early allocations") Signed-off-by: Breno Leitao leitao@debian.org Reported-by: Jakub Kicinski kuba@kernel.org Acked-by: Catalin Marinas catalin.marinas@arm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/kmemleak.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/kmemleak.c~mm-kmemleak-avoid-deadlock-by-moving-pr_warn-outside-kmemleak_lock +++ a/mm/kmemleak.c @@ -470,6 +470,7 @@ static struct kmemleak_object *mem_pool_ { unsigned long flags; struct kmemleak_object *object; + bool warn = false;
/* try the slab allocator first */ if (object_cache) { @@ -488,8 +489,10 @@ static struct kmemleak_object *mem_pool_ else if (mem_pool_free_count) object = &mem_pool[--mem_pool_free_count]; else - pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); + warn = true; raw_spin_unlock_irqrestore(&kmemleak_lock, flags); + if (warn) + pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n");
return object; } _
Patches currently in -mm which might be from leitao@debian.org are